The present invention relates to an arrangement in connection with a crosscutting saw of a harvester. Such an arrangement is intended for use particularly in connection with a crosscutting saw at a harvester head of a harvester moving in the terrain.
Since the tendency in modern harvesters is towards an optimally short time taken up by crosscut-sawing, there is a continuous trend in the field to increase the speed of rotation of chainsaws and, at the same time, the peripheral speed of the therein provided chain up to the maximum values set by the chain manufacturer. The ever-increasing speed of the chain increases the risk of the chain breaking during sawing or pieces being detached from it. If the chain breaks, it may cause a so-called chain blast, wherein the chain or parts thereof are thrown into the surroundings of the chainsaw with a high force and speed causing a significant safety risk in the working environment. There exist distinct findings that the number of such accidents has increased significantly.
However, the saw casing of a chainsaw cannot be made entirely enclosed, even if that prevented such problems or at least significantly lessened the risks caused by a dangerous chain blast. When a tree trunk is felled or crosscut-sawn, much sawdust is produced, which is packed inside the saw casing during sawing. The problem is particularly emphasized in winter conditions when not only sawdust, but also snow is packed inside the saw casing. Accordingly, sawdust and snow would rapidly fill an encased saw casing, finally using up all the space required for the movement of the chainsaw. This is why prior art saw casings comprise a relatively open structure at that end of the chainsaw where the guide bar is hinged to the harvester head.
Attempts have been made previously to solve this problem, whereby device parts are known that are arranged in connection with the crosscutting saw at the harvester head of the harvester and used to attempt to prevent the chain of the crosscutting saw or parts thereof from being thrown in directions hazardous to the driver or objects or people in the environment. For example, patent publication WO 02/071833 discloses a solution wherein one or more movably arranged guarding members are arranged in connection with the saw casing substantially on the same plane as the rotational movement of the chain of the crosscutting saw. In the solution according to said patent publication, these guarding members are, however, arranged movable. Accordingly, the guarding members are kept in different positions when felling a tree and when cutting the tree into logs. The purpose of this solution is to achieve a protective effect as covering as possible, but at the same time, attempt to prevent any damage to the guarding members during delimbing, for example. The solution presented does lead to a complex structure and will probably restrict the usage of the harvester head. The use of the guarding member according to the solution does not, in spite of it all, bring about a complete security about the chain, when breaking or becoming detached from the sawing device. The previous guard member does not prevent a so-called chain blast in hazardous directions, since the tip of the guide bar of the crosscutting saw still propagates unprotected during most of the sawing.